Her mother had been afraid that if they ended up in regime hands they would be arrested, tortured, or worse.

People’s fears of revenge attacks appeared to have become a reality. The UN reported that more than 80 civilians had been killed by pro-government forces in the last 48 hours.

Syrian troops and allied Iraqi militias had entered homes after recapturing them and had executed residents "on the spot".

"The reports we had are of people being shot in the street trying to flee and shot in their homes," said Rupert Colville, a spokesman for the UN human rights office. "We're filled with the deepest foreboding for those who remain in this last hellish corner."

Some 11 women and 13 children were killed in four different neighbourhoods. One family of eight was reportedly executed in their home in the Bustan al-Qasr neighbourhood after refusing to leave.

More than 6,000 men and boys have been reported missing since mid-November after crossing from east Aleppo into the government-held western side of the city.

Women and children flee the neighbourhood of Bustan al-Qasr on TuesdayCredit:
AFP

The UN has pushed the Syrian government to allow monitoring of its treatment of fleeing civilians, including those who have been detained.

Screening by Syrian government forces of people leaving the city must itself be monitored, Mr Colville urged.

"It needs international eyes on the situation if the fears of the worst kinds of things happening - summary executions, torture, etc - are to be allayed," he said.

Syrian government forces and allied militias have been pushing to retake the whole of Aleppo for a month. Hundreds of people have been killed in shelling and bombing since the lightning offensive began.

My name is Bana, I'm 7 years old. I am talking to the world now live from East #Aleppo. This is my last moment to either live or die. - Bana

But civilians had been living under siege, with little food or medical care, since August, when the army captured the last road out.

Residents had pleaded for foreign governments to intervene and accused their allies of abandoning them to their fate.

“In other massacres and in other wars, like Srebrenica, they can perhaps claim they did not know,” said activist Monther Eatky. “They cannot claim that here. We have documented every war crime, every chemical attack. This was happening in real time in front of the eyes of the world.

“But still they did nothing.”

The US, which has spent the last five years calling for Assad’s removal, had been reduced to negotiating with Russia over how to evacuate the remaining civilians out of opposition territory.

The West's half-hearted approach to Syria's civil war - giving support to rebel forces, but never enough to beat the government or its Russian allies - was “an unmitigated failure,” Middle East analyst Peter Apps opined.

“Perhaps the US and UK should share the guilt for the horror that has come with it.”